An aminochromone compound is a useful compound as a pharmaceutical intermediate (e.g. Eur. J. Med. Chem., 32, 547(1997), JP-A 3-95144, etc.) and a known process for producing said compound comprises reacting a nitrochromone compound with hydrogen in the presence of a palladium catalyst (e.g. J. Chem. Soc. (C), 2230(1970), etc.). However, such a process is unsatisfactory as an industrial production process because it has a tendency to produce over-reduced compounds, wherein the carbon-carbon double bond at the 2-position and/or the carbonyl group at the 4-position of a nitrochromone compound are also reduced in addition to the nitro group, as byproducts and therefore the yield of the aminochromone compound thus obtained is low.
Another known process of synthesizing a compound having a chromone skeleton comprises hydrolyzing a dicarboxylic acid compound obtained by addition reaction of an expensive acetylene compound and a phenol compound to obtain carboxylic acid and then cyclizing said carboxylic acid to obtain a chromone compound (Aust. J. Chem., 48, 677(1995)). However, said process is not necessarily satisfactory industrially because it requires an expensive acetylene compound. Further, as a process for producing a nitrochromone compound, a process involving a use of nitro-substituted 2-hydroxyacetophenone as a starting material (JP-A 3-95144) is known and the nitro-substituted 2-hydoxyacetophenone is produced by nitration of 2-hydroxyacetophenone. However, position-selectivity for the nitro group-introduction in the nitration is low and as a result, isomers with nitro groups at different substitution positions are produced as byproducts. Therefore, a step of removing the isomers is required and thus said process involving a use of nitro-substituted 2-hydroxyacetophenon as a starting material is not necessarily an industrially satisfactory process.